[cmake-developers] cmake -E capabilities [v3]

[Tobias Hunger]

Hi CMake developers,

I am back to a internet-connected world, so here is a new update of
the cmake -E capabilities patch.

I did the changes Brad requested:
* Rebased on cmake master branch
* Add documentation
* Add a smoke test that makes sure that "cmake -E capabilities" can run.

Code is on github again:

https://github.com/hunger/CMake/commits/cmake-capabilities

Best Regards,
Tobias